Electrochemical system for analyzing performance and properties of electrolytic solutions

ABSTRACT

The invention relates to the analysis of the performance and properties of electrochemical processes, and specifically, to electrolytic solutions and electrode processes. The invention discloses a device and a method for obtaining qualitative and quantitative information for the kinetics of the electrode reactions, the transport processes, the thermodynamic properties of the electrochemical processes taking place in the cell. When a deposition reaction takes place, the device provides also valuable information about the relationship between the current density and deposit properties including but not limited to the deposit color, luster, and other aspects of its appearance. The device disclosed herein typically is comprised of a multiplicity of cathodic or anodic regions where one or more electrochemical reactions take place simultaneously, but at a different rate. From the precisely measured segmental currents one can obtain among other process properties: (1) An accurate relationship between the deposit appearance and the current density. This relationship can be used for process diagnostics, troubleshooting, control of concentrations, pH, and additives and contaminants and for optimizing the operating conditions, including the voltage, current, and circulation rate. (2) Quantitative determination of important process parameters including but not limited to, kinetics (e.g., exchange current density, cathodic and anodic transfer coefficients), transport (e.g. conductivity), and thermodynamics (e.g., standard potential). A particularly attractive application of the process is for the quantitative and qualitative processes of alloys plating and for the determination of the relationship between the current efficiency and the applied current density.

RELATED APPLICATIONS

[0001] This is a Continuation-in-Part application of U.S. applicationSer. No. 10/267,505 having a filing date of Oct. 9, 2002.

REFERENCES CITED

[0002] U.S. Patent Documents   2149344 March, 1939 Hull 204/153.  2760928 August, 1956 Ceresa 204/434.   2801963 August, 1957 Hull etal. 204/434.   2859166 November, 1958 Grigger 204/DIG.   3121053February, 1964 Hull, Jr. et al. 204/434.   3215609 November, 1965Chapdelaine 204/434.   3278410 October, 1966 Nelson 204/290.   3281338October, 1966 Leary et al. 204/290.   3356597 December, 1967 Schmidt204/434.   3616287 October, 1971 Draghicescu et al. 204/DIG.   4102770July, 1978 Moriarty et al. 204/212.   4252027 February, 1981 Ogden etal.  73/826.   4605626 August, 1986 Beck 204/403. 5,228,976 July, 1993Abys et. al. 5,413,692 May, 1995 Abys et al. 6,113,771 September, 2000Landau et. al.

OTHER REFERENCES

[0003] 1. Cell-Design©, Software for computer-aided-design ofelectrochemical cells, L-Chem Inc, 13909 Larchmere Blvd. Shaker heights,OH 44120. Website: www.L-Chem.com

[0004] 2. I. Kadija, J. A. Abys, V. Chinchankar and K. Straschil,“Hydrodynamically Controlled “Hull Cell”, Plating and Surface Finishing,July, 1991.

[0005] 3. Autolab HT RotaHull, designed by D. Landolt and C. Madore,manufactured and distributed by Eco Chemie, BV, Utrecht, TheNetherlands.

[0006] 4. J. S. Newman, Electrochemical Systems, Prentice-Hall, Inc.,Englewood Cliffs, N.J. (1973).

[0007] 5. A. J. Bard and L. Faulkner, “Electrochemical Methods”, JohnWiley and Sons, N.Y. 1980.

[0008] 6. Venjamin G. Levich, “Physicochemical Hydrodynamics”,Prentice-Hall, Englewood Cliffs, N.J., 1962.

[0009] 7. Uziel landau, “Determination of Laminar and Turbulent MassTransport Rates in Flow Cells by the Limiting Current Technique”, AIChESymposium Series 204, Vol. 77, pp. 75-87, 1981

BACKGROUND OF THE INVENTION

[0010] 1. Field of the Invention

[0011] The invention relates to the field of analyzing the properties ofelectrolytes and testing the performance of electrochemical processes.The invention focuses on electroplating processes, although it can alsobe directly applied to other electrolytic processes including, but notlimited to, electrowinning, electrorefining, and anodizing.

[0012] 2. Background of the Invention

[0013] The performance of electrochemical systems depends on the designof the cells in which the electrochemical reactions take place and onthe appropriate selection of the operating conditions, includingcurrent, voltage, electrolyte composition, species concentrations, flow,etc., to produce the desired results. The selection of the operatingconditions is particularly critical in plating cells where the depositthickness distribution and properties (e.g., appearance, color, surfacetexture, adhesion, and composition) strongly depend on the cellconfiguration and the process parameters. In order to obtain adequatequality product, practitioners often utilize two approaches: (i)experimental—a test fixture or apparatus e.g., the “Hull cell”[described e.g., in U.S. Pat. Nos. 2,149,344, 2,801,963, 3,121,053] isused to generate, by specifying and controlling the total current, asample that is plated under a range of current densities. The sample isvisually inspected and correlated with the process conditions; (ii)modeling—where the electrochemical process is mathematically analyzedand the conditions to produce the desired results are sought. In recentyears, the latter approach has been enhanced by simulations usingcomputer-aided-design (‘CAD’) software e.g., Cell-Design© [Ref. 1].Knowing the process parameters (e.g., kinetics constants, standardpotential, and conductivity) is an essential prerequisite for themodeling approach. Yet, this data is typically not available,particularly not for commercial electrolyte formulations, and generatingthis data is quite onerous.

[0014] As discussed below, both these approaches (‘experimentaldeposition onto a test fixture’ and ‘modeling’) suffer at present from anumber of shortcomings that the invention disclosed herein resolves.

[0015] Limitations of the Current Approaches:

[0016] A. Limitations of Special Fixtures and Devices that CharacterizeDeposits Produced Under a Range of Current Densities

[0017] The most commonly used device to experimentally explore a depositproduced under a range of current densities is the ‘Hull cell’ [U.S.Pat. Nos. 2,149,344, 2,801,963, 3,121,053]. The Hull cell, shown in FIG.1A, is a prismatic cell with vertical insulating sidewalls, an anodepanel (2) and a slanted cathode panel (3). Due to the different anglesof the corners between the slanted cathode and its neighboringinsulating sidewalls (acute angle (4) at one side of the cathode and anobtuse angle (5) at the other side), and the varying distance betweenregions on the cathode and the anode, the deposit is plated on thecathode under a non-uniform current density: the highest current density(and correspondingly, the thickest deposit) is near the corner with theobtuse angle (5); the lowest current density (and thinnest deposit) isnext to the corner with the acute angle (4). The current density and thecorresponding deposit thickness vary between the two corners in anon-linear fashion. Since, only the total current to the entire cathodecan be measured in the Hull cell, users are given a scale (6), shown inFIG. 1B, on which the expected current density is indicated as afunction of position. By placing this scale alongside the cathode panel(3), as shown in FIG. 1B, users can estimate the current density thatcorresponds to the deposit at the given location. The major deficiencyof the Hull-cell is that the current density indicated on the scale isonly a rough approximation. This approximation is inherent and cannot beimproved because the current distribution does not depend only on thecell geometry, as implied in the Hull-cell description, but it varieswith the type of plating solution used. For example, lead and zincdeposition produce a highly non-uniform distribution; copper platingproduces a moderately uniform distribution, and nickel, iron and goldproduce significantly more uniform distribution. The curves displayed inFIG. 2 show the computed current density distributions in typicalelectrolytes (copper from acidified copper sulfate, and Watts-typenickel), as modeled by Cell-Designo CAD software, in comparison to thecorresponding value indicated by the Hull cell scale. As noted in FIG.2, even for those very common electrolytes, significant differences(exceeding 25%) at the low and high current density ranges exist. Aneven more serious obstacle to using the Hull cell for the selection ofthe proper operating conditions is the variation of the currentdistribution due to variations in the electrolyte's temperature, ionicconcentrations, conductivity, additive concentration, contaminants andby-products, which are supposed to be analyzed by the Hull cell test,yet their effects on the current density is not indicated. Accordingly,there exists a significant uncertainty in matching the deposit at anygiven location along the Hull-cell cathode to the actual prevailinglocal current density. Furthermore, the deposit thickness variesgradually and continuously along the cathode. Since the user relies onvisual inspection of the deposit to determine whether the appearance ofthe latter is satisfactory, it is difficult to clearly differentiate theacceptable range.

[0018] Another device that is occasionally used to determine theproperties of the plating electrolyte is the Haring-Blum cell. Here, twoparallel cathodes are positioned at two different distances, on bothsides of a common anode. The ratio of the deposit weights on thecathodes characterizes the throwing power of the electrolyte, which isproportional to the ratio between the deposition reaction resistance andthe electrolyte resistance. While the Haring Blum cell provides thethrowing power (or the resistance ratio) at only one current density ineach experiment, there is a need to provide this ratio across a broadrange of current density in a single experiment.

[0019] Two variations on the Hull cell have been subsequently suggested.One is the Casey-Asher cell which has an elongated rectangularcross-section, where the non-uniform deposition takes place along one ofthe elongated electrodes. The second is the pie-shaped Tena cell,consisting of two concentric cylindrical insulating walls bound by tworadially positioned planar electrodes. Both of the variations on theHull cells, while not widely used, suffer from the same deficiencies asthe Hull cell.

[0020] More recently, Abys et. al. introduced the ‘hydro dynamicallymodulated Hull cell’ [Ref. 2 and U.S. Pat. Nos. 5,228,976 and5,413,692], which was designed to provide improved and better quantifiedmass transport. The cell consists of a cylindrical rotating cathode andan anode positioned to provide a non-uniform current distribution.Specially positioned baffles help adjust the current distribution. Thiscell suffers from the same limitations that apply to the Hull cell,i.e., it provides a distribution that depends on the electrolyte typeand composition, and not just on the geometry. Furthermore, since onlythe total current is measurable, the deposit at any given location alongthe cathode cannot be precisely associated with a specific currentdensity. Another very similar cell that has recently been introduced byLandolt and Madore [Ref. 3], has identical features to Abys' et. al.cell and suffers from the same shortfalls.

[0021] None of the cells described above provides any quantitativeinformation concerning the physical and/or chemical parameters of theprocess.

[0022] B. Difficulty in Obtaining Electrochemical Process Parameters

[0023] A major impediment to applying quantitative modeling (bothanalytical and computer-aided design) to electrochemical systems is thepaucity of available property data that such modeling requires.Typically, thermodynamic, kinetics, and transport properties are neededin order to characterize the processes that take place inelectrochemical cells. These processes can be generally divided into twomajor categories: (a) processes associated with the electrode reactionsand (b) ionic transport in the electrolyte.

[0024] The electrode processes are quite complex and typically involvenumerous steps that are difficult to unravel. Their characterizationcan, however, be accomplished without detailed mechanistic knowledge byspecifying the global thermodynamics and kinetics parameters. However,obtaining this data is typically quite difficult. The thermodynamicsproperties include the standard reaction potential (E⁰) whose value canbe found in standard thermodynamic tables. However, the actualequilibrium potential (E) depends also on the temperature, theelectrolyte concentration (ionic activities) and particularly on thecomposition, including species that complex the reacting ion and thatmodify the adsorption properties on the electrode. Determination of theeffects of all these parameters is quite difficult and requires at thebare minimum the use of a special, well characterized, referenceelectrode [Refs. 4, 5]. Specification of the electrode kinetics requiresa polarization curve that describes the dependence of the electrodeoverpotential (=potential exceeding the equilibrium potential due toirreversible dissipative processes, e.g., kinetics resistance) as afunction of the current density. Commonly, the polarization curve isrepresented in terms of the Butler-Volmer equation, which has somefundamental justification, but in practice serves mostly as acorrelation, i.e., the parameters are determined empirically throughpolarization experiments. Although the physical significance of theparameters in this equation can be attributed only in very few simpleprocesses, the general form of this equation and its three adjustableparameters (exchange current density [i₀], anodic [α] and cathodic [β]transfer coefficients) that are measured empirically, have enabled tomodel numerous electrochemical processes. The general application of theButler-Volmer equation, or other polynomial correlations that have beensuggested, from data in the literature is, however, limited because ofthe interdependence of the electrode kinetics on the transport, andparticularly on the reactant (and additives) concentration at thesurface. These in turn, depend not only on the convective and diffusivetransport but also on the current density, both of which typically varyalong electrodes and with operating conditions.

[0025] Ionic transport in the electrolyte involves diffusion, migrationand convection. Its simulation requires knowing the ‘integral’ diffusioncoefficient of the reacting species. The latter can be measured on arotating disk electrode assembly as introduced by Venjamin Levich in hisbook “Physicochemical Hydrodynamics” published by Prentice-Hall,Englewood Cliffs, N.J., 1962, which is incorporated herein by reference[6]. The experimental set-up is, however, costly. It requires a rotatingdisk electrode assembly, a power supply with current/voltage rampcapability and data recording capability. The process of generating thedata is time consuming, and requires expertise as described, e.g., in apaper by Uziel Landau, “Determination of Laminar and Turbulent MassTransport Rates in Flow Cells by the Limiting Current Technique”, AICHESymposium Series 204, Vol. 77, pp. 75-87, 1981, which is incorporatedherein by reference [7]. In addition, one needs to characterize the masstransport process in the cell. This typically amounts to specifying themass transport boundary layer thickness, and its distribution in thecell, or equivalently, the limiting diffusion current. These are quitedifficult to determine since they depend on detailed characterization ofthe flow in the cell and on the cell configuration, typically requiringcomputational fluid dynamics modeling. Even where forced convection isnot present or is not dominant, determining the characteristics of thediffusion flux in complex geometries is difficult.

[0026] Ionic transport also proceeds via electric migration that ischaracterized by the conductivity. The latter varies with theelectrolyte composition, concentration (i.e. it is affected by the localcurrent density or concentration gradients), and temperature.

[0027] In addition to the difficulty in characterizing the details ofthe electrochemical process so that proper parameters can be assigned,there is a difficulty in obtaining the data and in particular, thekinetics parameters (e.g., i₀, α and β, as described above). Theliterature typically offers only rate constants for pure elements (andeven those are given for only one standard concentration or activity).Practical processes, and in particular plating systems, employ complexchemistries, incorporating additives and complexing agents that stronglyaffect the deposition kinetics, as described e.g. by U. Landau et. al.,in U.S. Pat. No. 6,113,771. It is therefore required in almost allpractical situations to experimentally measure the parameters for thegiven system. Such measurements require, however, special cells that arespecifically designed for the type of measurement. Examples includeconductivity cells coupled with high frequency analyzer for conductivitymeasurement, and rotating disk electrode for measurements ofdiffusivity. The rate constants, i₀, α and β, must be typically obtainedby conducting a sweep of a current-potential scan in cells that aredifficult to design because of the requirement for (a) a uniform currentdensity on the tested electrode (otherwise a meaningless average isdetected), (b) uniform and tractable transport rates to the electrode,(c) means of detecting and subtracting the ohmic and concentrationoverpotentials, and (d) a three electrode system incorporating areference electrode so that the potential of the test electrode can beelucidated. Special and costly power supplies (‘potentiostats’) that arecapable of three-electrode voltage control versus a reference electrodeare also required. The kinetics constants are typically extracted frompolarization curves, hence a dynamic measurement in which the cellvoltage or current are ramped by the power supply over sufficiently widerange must be implemented. These experimental procedures are describedin the literature, e.g., in a book by Allen Bard and Larry Faulkner,“Electrochemical Methods” published by John Wiley & Sons, NY, 1980,which is incorporated herein by reference [5]. The special experimentaltechniques require procedures that many practical engineers are notproficient in, nor have the time to learn and carry out.

SUMMARY OF THE INVENTION

[0028] The present invention relates specifically to testing,characterization, and obtaining quantitative data for processes takingplace in electrochemical cells. It provides innovation in two majoraspects: (1) describing a device with multiple discrete electrode sitesat which electrochemical reactions proceed simultaneously at differentand precisely measured rates (=current densities). In a preferredembodiment, the reaction produces under precisely measured differentcurrent densities, multiple discrete deposit patches, which can then bestudied visually and analytically (using analytical instrumentation,e.g., x-ray or electron microscopy), and thus provide a correlationbetween the appearance of the deposit and the current density at whichit was produced. By comparing the measured deposit thickness on thedifferent segments to their local current density, a measure of thecurrent efficiency as function of the current density is obtained. Whenan alloy is deposited, measuring the segmental composition will yieldthe partial current densities for each component. (2) A method forextracting essentially the entire quantitative data needed to model theelectrochemical system from a single deposition experiment carried in adevice that provides simultaneously different current densities onseparate electrodes or electrode segments, such as the device disclosedabove. The data derived includes the equilibrium potential, thepolarization curve and the associated kinetics constants (i₀, α, β), andthe electrolyte conductivity. In alloy deposition, when the segmentalcompositions are measured, the kinetics for the entire alloy system canbe obtained from this single experiment. Such alloy data cannot begenerated by the corresponding current/potential scanning experiment.

[0029] The key to the invention is the provision of numerous discreteregions on the same substrate, each carrying a different, measurablecurrent density. This provides precise deposit patches, eachcorresponding to a different and precisely known current density.Furthermore, since both the (different) current densities and thevoltages across each of those regions are measured, the data generatedin a single experiment provides a multi-point correlation between thecurrent density and the potential, i.e., this single steady-stateexperiment is the equivalent of an entire conventional current-voltagescan. The data collected in this single experiment can also yield theconductivity and the equilibrium potential. Among the advantages of theinvention is that the extensive data can be generated in a single,simple, steady-state experiment. It does not require expensiveinstrumentation or electrochemical expertise, and the need for atime-dependent current/voltage scan and its associated complications, iseliminated. Transforming the experiment from a time domain of sweepingthe current into the spatial domain of measuring a steady-statedistributed reaction rates, offers numerous advantages. First, issues ofunsteady-state and transients in the measurements are eliminated. Whenthe current/voltage is scanned in a conventional experiment, the scanrate should not be too slow, in order to avoid deposit build-up which,particularly when rough, may alter the electrode morphology and area;nor should the scan be too fast, in order to avoid unsteady-state andtransient effects. Also, unlike in the device disclosed herein,conventional scanning of the current (or voltage) produces a depositthat had been accumulated over a range of current densities; hence it isno longer useful for inspection.

[0030] Some aspects of the invention are also useful forcharacterization of electro-dissolution, electropolishing, and corrosionprocesses. For clarity, the discussion henceforth focuses onelectroplating. Primarily, the invention addresses the difficulty indetermining the properties of electrolyte solutions and on predictingthe effects of the process conditions on the product, i.e., on thedeposit. Although the main application of the invention is forelectrodeposition systems in which a deposit builds up on the substrate,the device and method claimed herein are also useful for analyzingelectrochemical processes in which no solid deposit forms.Electrochemical reactions that fall under this category includeelectrolytic manufacture of gaseous and liquid chemicals, redoxreactions, electrolytic gas evolution, various electrodissolutionprocesses and corrosion. In the absence of a deposit, the claimed deviceand method will still yield for those processes the electrochemicalprocess parameters, i.e., the thermodynamic, kinetics and transport datathat are required for modeling these processes.

[0031] According to the present invention, there is disclosed anelectrochemical device, comprising a cell with a plurality of discretecathodic or anodic regions at which one or more electrochemicalreactions occurs; and means for causing the one or more electrochemicalreactions at each of the plurality of discrete regions whereby each ofthe one or more electrochemical reactions is measurable andquantifiable.

[0032] Further, according to the present invention, an electrochemicaldevice for simultaneously forming a plurality of electroplated depositsat a plurality of discrete cathodic or anodic regions at which one ormore electrochemical reactions occurs comprises a cell with base, anenclosure such as a cover or a mask, and a plated, segmented substratethe substrate having a plurality of discrete cathodic or anodic regionsat which one or more electrochemical reactions occurs clampedtherebetween.

[0033] Still further, according to the present invention, process fordetermining the quality of electroplated deposits comprisessimultaneously depositing a plurality of discrete deposits, each at oneof a plurality of discrete cathodic or anodic regions at which one ormore electrochemical reactions occurs; and causing the one or moreelectrochemical reactions at each of the plurality of discrete regionswhereby each of the one or more electrochemical reactions is measurableand quantifiable.

[0034] Further yet, according to the present invention, a method isdisclosed for determining electrochemical process parameters fromcurrents or voltages measured while at least one electrochemicalreaction takes place at different measurable rates on a plurality ofdistinctly different cathodic or anodic regions in an electrochemicaldevice.

BRIEF SUMMARY OF THE FIGURES

[0035] Reference will be made in detail to preferred embodiments of theinvention, examples of which are illustrated in the accompanying drawingfigures. The figures are intended to be illustrative, not limiting.Although the invention is generally described in the context of thesepreferred embodiments, it should be understood that it is not intendedto limit the spirit and scope of the invention to these particularembodiments.

[0036] Certain elements in selected ones of the drawings may beillustrated not-to-scale, for illustrative clarity. The cross-sectionalviews, if any, presented herein may be in the form of “slices”, or“near-sighted” cross-sectional views, omitting certain background lineswhich would otherwise be visible in a true cross-sectional view, forillustrative clarity.

[0037] The structure, operation, and advantages of the present preferredembodiment of the invention will become further apparent uponconsideration of the following description taken in conjunction with theaccompanying drawings, wherein:

[0038]FIG. 1A is a prior art prismatic Hull-cell;

[0039]FIG. 1B is a card on which the expected current density isindicated as a function of position for a prior art Hull cell;

[0040]FIG. 2 is a graph showing the curves of the computed currentdensity distributions in typical electrolytes;

[0041]FIG. 3A is an orthogonal view of an embodiment of a cell deviceconsisting of an electrode substrate with multiple electrode segments,according to the present invention;

[0042]FIG. 3B is a partially transparent view of the device showing someinternal features of the cell device according to the present invention;

[0043]FIG. 3C is an orthogonal view of a cover of the cell device ofFIG. 3A according to the present invention;

[0044]FIG. 3D is an orthogonal view of the base the cell device of FIG.3A according to the present invention;

[0045]FIG. 3E is a front view of the plated substrate shown in FIG. 3D;

[0046]FIG. 3F is a cross sectional view through line A-A of FIG. 3Eshowing the plated substrate;

[0047]FIG. 3G is a top view of the cell device of FIG. 3A, showing theprojections of the key cell components;

[0048]FIG. 3H is a cross sectional view through line B-B of FIG. 3G;

[0049]FIG. 4 is a schematic view of the cell device of FIG. 3A immersedin a beaker according to the present invention;

[0050]FIG. 5A is an orthogonal schematic view of a segmented rotatingdisk electrode according to another embodiment of the invention;

[0051]FIG. 5B is an orthogonal schematic view of a rotating segmenteddisk electrode surrounded by a ring electrode according to anotherembodiment of the invention;

[0052]FIG. 6A is an orthogonal view of the cell device configured as acylinder according to another embodiment of the invention;

[0053]FIG. 6B is an orthogonal view of the cell device configured as acylinder according to another embodiment of the invention;

[0054]FIG. 7 is a side view of a cell device configured as part of aflow channel, according to another embodiment of the invention;

[0055]FIG. 8 is an orthogonal view of a cell device without an anodeaccording to another embodiment of the invention;

[0056]FIG. 9A is a diagonal view, showing a cross-section with some keyinternal features of a cell device designed to function as a tabletopinstrument according to another embodiment of the invention;

[0057]FIG. 9B is a partially transparent side view showing some keycomponents of the tabletop cell device of FIG. 9A;

[0058]FIG. 9C is a cross sectional top view through line A-A of FIG. 9Bshowing some of the components;

[0059]FIG. 9D is a cross sectional front view through line B-B of FIG.9B showing some of the components;

[0060]FIG. 9E is a front view of the plating mask shown in FIG. 9A;

[0061]FIG. 9F a front view of the plated test panel shown in FIG. 9A;

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0062] The present invention generally relates to a device consisting ofan electrode substrate with multiple electrode segments. The device isimmersed in an electrolyte and the current turned on for a period thatcan range from, typically, a few seconds to many minutes. The differentcurrents to each of the electrodes or electrode segments are measured,and provide, after computations, the process parameters detailed above.The invention also teaches a simple method for setting the differentcontrolled segmental currents, although other methods may be used aswell, for obtaining similar current ranges. To increase the range ofmeasurements, different voltages or currents can be sequentiallyapplied. The invention further discloses a method that enables theutilization of said currents to yield quantitative data characterizingthe electrochemical process. In a preferred embodiment, the inventioncomprises a special fixture that holds a segmented electrode substrate(here, the cathode), exposing to the electrolyte well-defined regions onsaid electrode. The device further incorporates multiple terminalcontacts, typically, one to each segment, that are adjusted to deliverand measure a different current density to each segment. The inventionalso discloses a special computational approach to determine from saidmeasured segmental currents, critical electrochemical process parametersincluding the polarization curve and its associated kinetics constants,the electrolyte conductivity and the equilibrium potential.

[0063] Typically, the device is designed, by selecting the configurationand dimensions of the cavities through which the electrode segments areexposed to the electrolyte, such that the current density and thereforealso the deposit properties within each of the distinct regions isrelatively uniform. Although this uniformity is not a requirement forthe disclosed device (and in certain applications a non-uniformdistribution may be advantageous), typically this design for uniformityis an advantage. One means of achieving uniformity is by havingrelatively high-aspect ratio holes, e.g. ratio of depth to diameter ofthe order of 1 or more.

[0064] An important parameter for electrochemical process analysis, andparticularly for plating, is the current efficiency, i.e. the fractionof the passed current that contributes to the actual deposit. Thiscurrent efficiency typically varies with the prevailing current density.The determination of the current efficiency can be made by comparing theprecisely measured segmental currents to measurements of thecorresponding deposit thickness or weight on the different plated‘patches’.

[0065] Further understanding of the present invention will be had withreference to the following examples, which are set forth herein forpurposes of illustration but not limitation.

EXAMPLE 1

[0066]FIG. 3A is a schematic drawing of a device that incorporatesfacets of the invention disclosed herein. FIG. 3A shows an overall view,FIG. 3B is a partially transparent view of the device showing someinternal features of the cell. FIG. 3C shows the cover of the cell in anupside-down view, revealing the separate contacts and the cavities. FIG.3D is a view of the bottom part of the cell with the top removed,showing the plated segmented substrate. FIG. 3E shows a schematic topview of the plated segmented cathode, and FIG. 3F is a cross-section(not to scale) of same substrate. FIGS. 3G and 3H are cross-sections ofthe device. The specific device described herein is about 2 inches wide,5 inches long and about 1.5 inches high. It is understood that differentsizes may be applied. Following is a detailed description of the device.

[0067] The device consists of two major parts as shown in detail inFIGS. 3C and 3D: a base (8) shown in detail in FIG. 3D, and a cover (9),shown in detail in FIG. 3C. The base and cover are both made of a rigidinsulating material, e.g., a ceramic or a plastic, and in thisparticular embodiment, polyvinyl chloride (PVC). Other materials thatcan be used include, among others, Plexiglas, epoxy, and Teflon. Aconducting material can also be used, however, in this case it must becoated with an insulating film. The base incorporates a slot (25) thathelps position the plated segmented substrate (7), as shown in FIG. 3D.This slot is not an essential part of the example and is provided forconvenience in positioning the plated substrate. Other guides, madee.g., of an elastomeric or a rigid plastic frame can replace it. Asshown in FIG. 3D, the base also incorporates threaded posts (27) thatprovide positioning and tightening of the cover, (9), using the knurlednuts (13) that are shown in FIG. 3A. The base also incorporates,optionally, bumpers (29) at its front to protect the protruding portionof the plated substrate.

[0068] An insulated substrate (7) coated with a thin and segmentedconductive seed layer has is clamped between the base (8) and the cover(9), as shown in FIGS. 3A, 3B and 3D. The plated substrate is shownschematically in FIG. 3E (top view) and 3F (cross section). In order toillustrate details, these drawings are not to scale. A typical size ofthe substrate is about 1.5″ wide and about 3.5″ long, although othersizes may be used. The substrate thickness is not very important and mayvary, however {fraction (1/16)}″ may provide a typical value. Thesubstrate bulk (31) in FIG. 3F, may be made of any of a variety ofelectrically insulating (dielectric) materials. An example is silicon,glass or a plastic material such as used in printed circuit boards,e.g., polyimide. The conductive seed layer on top of the insulatingsubstrate (35) may consist of e.g., copper, nickel, brass, gold, or anyother conductive layer that is compatible with the electrochemicalprocess to be tested. The thickness of the said layer range from verythin e.g., 500 Angstrom to a mm or more. However, the minimal thicknessmust be such that it provides a continuous conductive layer. Metalliclayers below about 100 Angstroms are known to agglomerate, which is notdesirable. The conductive seed may be deposited on the substrate using,most commonly, a vapor phase process (e.g., evaporation, physical vapordeposition, chemical vapor deposition), an electroless process, or bylamination or gluing of a conductive film onto the dielectric substrate.Said seed layer in the present example is segmented, i.e., consists ofelectrically isolated sections (35). Separating grooves to isolate thesegments are indicated by (18) and shown in FIGS. 3B, 3E and 3F. Itshould be noted that instead of the insulating substrate coated withisolated electrode segments, completely separate electrode sections maybe used. Such separated electrodes may either consist of seed coveredinsulating substrate or be made entirely out of conductive material,such as copper, brass, or zinc. However, such separate electrodes maynot be as easy to handle and position as the one piece segmentedsubstrate, and therefore are less desirable. Cavities within the cover(9) define the plated regions, typically circles (20) shown in FIGS. 3D,3E and in the cross-section 3F. Also indicated faintly in FIGS. 3D and3E are the points of electrical contacts with each segment (21). Asshown in FIGS. 3B, 3D, 3E and 3F, the front edge of the cathode consistsof an un-plated but electrically contacted segment (19) that serves as areference electrode. Its role is discussed further below.

[0069] The device cover (9), which can be made of the same or differentmaterial as the base plate (8), incorporates cavities (10) that definethe areas through which the cathode segments are exposed to theelectrolyte and to the ionic current. An elastomeric (e.g., rubber)gasket (11) between the base and the cover may be beneficial inproviding a good seal around the cavities and accurately define thecircumference of the plated ‘patches’ on the seeded substrate. Thecavities shown here are of a round cross-section, however, otherconfigurations, including squares and rectangles can be contemplated.The size of the plated ‘patches’ is not critical, however, some minimalsize of e.g., a few mm in diameter or length, is beneficial in order tofacilitate visual inspection, if so desired. In the specific examplediscussed here, holes with a diameter of about ⅜″ and a depth of about{fraction (7/16)}″ were selected. The depth of the cavities ensures auniform current density across the exposed regions on each of thesegments. Furthermore, the depth of the cavity also controls themass-transport. For short deposition experiments, e.g., a few minutes,where depletion of the electrolyte within the cavity is not significant,the depth of the cavity beyond some minimal value, equivalent e.g., tothe diameter of the hole, to assure uniform current distribution andprovide a sufficient electrolyte reservoir, is not critical. However,for longer deposition experiments, or for experiments wheremass-transport effects are studied, the depth of the cavity must beproperly designed and accounted for in the model. An array of thin rods,(15), placed inside an insulating compartment (16) that is attached tothe top of the cover (9), penetrate through the bottom of the cover asshown in FIG. 3C and make contact with the metallic seed layer to beplated. These rod contacts provide a separate current feed to each ofthe segments. Their point of contact with the plated substrate isindicated by the faint circles (21). The contacts can be made from avariety of metals or alloys. Examples include, copper, stainless steel,titanium or their alloys. To ensure a low contact resistance, thecontact points may be optionally coated with platinum or gold. Thecontacts may be pressed against the cathode using a spring or acompressible pad made of e.g., elastomer, indicated by (17) in FIGS. 3Aand 3B. The role of the sealed compartment (17) is to support thecontact rods and provide of a region that is not exposed to theelectrolyte. Within that region, the electrical feed wires, (21), shownin FIG. 3G, are connected to the top portion of the rod contacts. Theelectrical wire bundle (37) is fed through a sealed wire feed (39) intothe compartment. The compartment (16) also supports the back portion ofthe anode (12) that is attached to it by small screws (41) as shown inFIGS. 3A, 3B, and in the cross-section 3H.

[0070] The counter electrode, which is not segmented, is in this examplethe anode (12). It may be a plate, perforated plate, or an expandedmesh, fixed at some distance away from the cathode. The anode can bemade of a number of conductors on which oxygen can evolve including:platinum, gold, titanium, titanium coated with iridium oxide orruthenium oxide or platinum, lead, or silver-lead alloy. Alternatively,soluble anodes made of e.g., copper or nickel, as appropriate for thetested electrolyte, may be used. A wire (42) in FIG. 3A provides thecurrent to the anode. The anode is supported in the configuration ofthis example in its front end by stand-off insulating rods (14), towhich the anode is fastened by means of a small screw (43). As discussedbelow, a variant of the present example, where an anode is notincorporated in the device can be equivalently contemplated. In thecase, externally provided anodes may be used. Typically, in this lattersituation, deeper, narrower cavities may be desirable, to minimize thevariability in the electrolyte resistance associated with differentdistances between the cathode and the external anode that can beexercised in different experiments.

[0071] The different current through each contact (and cathode segment)is set using special electronics circuit. The latter may consist of anumber of separate potentiostats or current limited power supplies. Alikely preferred embodiment is using a single power supply, butincorporating an array of operational amplifiers, voltage followers, oras incorporated in the present example, a number of current controllingresistors. If these external resistors are much larger than any otherresistance in the current path, i.e. much larger than the electrolyteresistance, the resistance attributed to the electrode reactions (onboth the anode and the cathode), and any mass transport resistance, thenthe current within any cathode segment will be controlled by thisexternal resistor. Furthermore, measuring the voltage drop across thisresistor provides a measure of the current in the given branch. In someapplications, it may be desirable to replace this one controllingresistor, by two resistors, where one may be a relatively small shunt,across which the segmental current can be determined by measuring thevoltage drop.

[0072] As noted in FIGS. 3A, 3B, 3D, 3E, and 3F, a section of thesubstrate (19), covered by an electrically isolated seed layer extendsbeyond the substrate holder. This extension serves the dual purpose ofaiding in inserting and removing the cathode, and also serves as areference electrode. Accordingly, this extension is connected to thevoltage-sensing device through a high impedance resistance so that noappreciable current flows through this segment and thus it is notplated. Obviously, other configurations of the reference electrode arepossible. Lastly, bolts (27), or other clamping hardware is used totightly clamp the cathode between the fixture bottom plate and cover.Holes in the cover, (47), provide clearance for the bolts. Knurled nuts(13) are used to tighten the fixture together.

[0073]FIG. 3G provides a top view of a cross-section through the device.The electrical connections (21) to the separate contacts (15), areshown. Also shown are optional pegs (29) to protect the protruding edgeof the substrate that can serve as a reference electrode, and a handle(23). The cross-sectional side-view in FIG. 3E shows details of theclamping bolts (27), the anode (12), the plated cavity (10), and thecontact (15), pressed by the elastomer (17) against the cathode (7).Lastly, sink nuts (28), at the bottom of the base provide support to thethreaded rods (27).

[0074] The device as shown schematically (not to scale) in FIG. 4 isimmersed in a beaker (50) containing a sample of the electrolyte to betested, or immersed in an industrial scale plating cell. The volume ofthe electrolyte to be tested is not critical; however, the electrolytelevel (52) must be sufficiently high to cover all the cavities throughwhich plating is to be done. A 200 ml beaker is typically adequate. Thepower supply (54) is turned on [by pressing switch (55)] for a fewseconds or minutes during which electrochemical reaction takes place,the deposit builds-up (at different rates) on the exposed areas of thecathode, and the data acquisition records the segmental currents andvoltages. The data acquisition can be computer-based, as shown (56) inFIG. 4. From the recorded data, the polarization curve (i.e., a plot ofsegmental current densities vs. the overpotential) is constructed. Inaddition, the electrolyte conductivity is determined, and theequilibrium potential established. The data is stored in the computerand can be displayed on the computer screen (57). The computations arebased on conducting voltage balances between each of the differentcathodic segments, the reference electrode, and the anode. The segmentalvoltage balance equations equate the voltage drop across the controllingresistances, when present, the cathodic standard potential, theactivation resistance associated with the cathodic electrochemicalreaction, the ohmic resistance in the electrolyte, the standardpotential at the anode and the overpotentials at the anode to theexternally applied voltage by the power supply. All those parameters,with the exception of the standard potentials, depend either linearly ornon-linearly on the current density, which is controlled and measuredindependently in each of the segments. The set of voltage balanceequations can be solved simultaneously to yield the electrochemicalprocess parameters listed above. The computations hinge on Cell-Design'scomputer implemented modeling of the cell, to provide the appropriateelectrolyte resistances that are used in the computation. However, theinvention herein can also work remotely of Cell-Design software, wheresaid constants are separately evaluated. Alternatively, empiricalcalibration of the cell herein, using well-characterized electrolyte,for which all the parameters are known, is possible. In this case, thecomputer-based model is no longer required.

[0075] A computer program computes the needed parameters (i₀, α_(A),α_(C), κ, E⁰) from the recorded data. The computed parameters and thepolarization curve are stored in a computer and can be displayedgraphically and numerically. They can also be incorporated in a databaselinked to electrochemical computer-aided-design software used formodeling electrochemical systems with the same electrolyte but adifferent configuration.

[0076] The beaker (50) into which the test fixture is immersed may beoptionally equipped with an immersion heater (not shown), or placed on ahot plate (not shown) to control its temperature. Agitation through amagnetic stirrer, bubble induced agitation using inert gas, or airsparged from e.g., a fritted glass, or convective flow using a pump mayalso be applied.

EXAMPLE 2

[0077] Another cell and electrode configuration that can be usedadvantageously when incorporating elements of the invention disclosedherein, is a segmented rotating disk electrode (RDE), as shownschematically (60) in FIG. 5A, or a rotating segmented disk electrodesurrounded by a ring electrode (62), as shown schematically in FIG. 5B.An insulating ring (64) separates the two. The ring electrode may serveas the reference electrode, a co-planar anode, or another auxiliaryelectrode whose potential is scanned and is used for analyzing productsor reactants of the electrochemical reaction [Ref. 5]. The segments canbe pie-shaped at the bottom of the rotating shaft (60), as shown in FIG.5A. This configuration works similarly to that discussed in example 1,however, it can provide also additional transport data. As shown byLevich [Ref. 6], the rotating disk provides a uniform and easilycalculable boundary layer thickness (or mass transport coefficient) thatdepends on the inverse square root of the rotational speed. By measuringthe parameters listed above (e.g., the kinetics parameters, at differentrotation speeds, the effect of transport on the kinetics parameters canbe determined, and the diffusivity can be evaluated.

EXAMPLE 3

[0078] The device disclosed herein can also be configured as a cylinder,as shown schematically in FIG. 6A and FIG. 6B. This configuration can beused similarly to the ones discussed above e.g., Example 1. It has,however, a number of advantages: it can be rotated to incorporate theeffects of transport, as in example 2, it can be designed in a compactform, to be used with small volumes, and furthermore, if configured as avery small diameter, it can present low transport resistance, since theradial diffusion flux is inversely proportional to the radius. Becauseof the electrode curvature, it can account for and simulate the effectof curvature on the deposit, e.g., incorporate effects of curvature onstress, and adhesion. The latter may be particularly important, becauseoften deposits that show marginal adhesion to a flat substrate mayadhere satisfactorily to a curved one. The segmental electrodes (66) canbe stacked one on top of the other as shown in FIG. 6A or the cylindercan be segmented radially (68), as shown in FIG. 6B. Otherconfigurations that involve bodies of revolution, e.g., cones, spheres,etc, can also be contemplated.

EXAMPLE 4

[0079] A variant of the fixtures described as examples 2 and 3 is aconfiguration whereby the central circular electrode, which can beeither a disk or a cylinder, is not segmented, however, the surroundingelectrode, which may be either the anode or the cathode, is segmented,and provides the multiplicity of electrodes claimed herein, that arediscussed in detail in example 1. By controlling the current density onthe different surrounding segments similar results to those described indetail in example 1 can be obtained for the surrounding segmentedelectrodes.

EXAMPLE 5

[0080] The device disclosed herein, can also be configured as part of aflow channel, as shown schematically in FIG. 7. Here, a cell with thesegmented electrode (7) is incorporated with, or inserted into a flowchannel through which the electrolyte is circulated. The measurementscan then be made at one or more flow rates. The advantage of thisconfiguration is that convective electrolyte flow can be adjusted tosimulate conditions in the actual processing cell, and also, the datacan be evaluated at different flow rates so that the effect of flow onthe other process parameters can be quantified. Additionally, thediffusion coefficient of the reacting species can be evaluated. In oneembodiment, the fixture described in example 1 is inserted into a‘manifold’ (80) that is incorporated within a flow loop, consisting of acirculation pump, an electrolyte holding vessel, a flow-meter and avalve for adjusting the flow (not shown). In the flow channelconfiguration the anode (12) can be part of the measurement cellfixture, as in example 1, or it can be part of the flow channel,embedded in its wall. A similar flow circuit can be incorporated inother device configurations, e.g., the base and mask of example 11 (FIG.9) can be similarly modified to incorporate flow.

EXAMPLE 6

[0081] A variation of the cell described in example 1 can becontemplated, where the anode, [(12) in FIG. 3], is not incorporated inthe fixture. Instead, the fixture (without the anode), schematicallyshown in FIG. 8, can be immersed in a production-type cell, or in a testcell, that incorporate their own anodes. In this case, the test fixturecan be connected to the existing anode through its own power supply, oruse an existing power supply that may already be connected to anexisting anode. The advantage of this embodiment of the invention isthat the testing and analysis can take place in the actual productionenvironment, under actual process conditions, eliminating the need totransfer electrolyte sample to a test beaker. The electrolytecharacterized this way resembles more closely the actual processconditions.

EXAMPLE 7

[0082] This example describes a configuration where the multiplicity ofelectrode segments are not necessarily located on a specific geometricconfiguration such as a plane substrate (example 1) a disk (example 2)or a cylinder (example 3). Here we bring forth the general notion thateach of the multiplicity of the controlled electrode segments can beseparately placed in any arbitrary location within a test fixture, atest cell or even a production cell. As long as the location of theelectrode is specified and it does not vary in an uncontrolled mannerduring the experiment, its current is well controlled and measurable,and its current density is different than that on a number of the otherelectrodes, a voltage balance can be carried out for each electrode.From this voltage balance, the polarization curve can be constructed andthe process parameters listed in the summary section and example 1 abovecan be computed in the same manner as described under example 1 above.Additionally, samples produced under different and precisely determinedcurrent density can be made available for visual inspection. Theseparate segments may consist of differently configured separateelectrodes. However, for accuracy, it is important that each electrodebe designed to experience a relatively uniform current density over itsarea. This can be achieved by e.g. embedding each electrode in aninsulating well, such as that used in the configuration discussed inexample 1. Another possibility is to use electrode segments that provideuniform current density. These may consist of spherical electrodes,hemispherical electrodes, or cylindrical segments. In thoseconfigurations, the counter electrode (e.g., the anode) must be placedfar away from the electrode segment on which the current density isbeing measured. ‘Far away’ here means about 3-5 diameters or more awayfrom the measured electrode. Alternatively, the counter electrode may beplaced closer; however, it must then be of the same geometricalconfiguration as the tested electrode. This implies that when placed inclose proximity, a cylindrical counter electrode must surround acylindrical controlled electrode, and a spherical counter electrode mustsurround a spherical controlled electrode.

EXAMPLE 8

[0083] Example 8 refers to situations where differently shaped or sizedelectrodes may be applied advantageously. An example is the situationwhere it is desired to apply the same overall current to each electrodesegment while it is needed for the invention disclosed herein to have,different current densities on each segment. Since the current densityis determined by the ratio of the total current to the electrode area,different current density may be achieved by varying the electrode areawhile maintaining the same total current. The rational for thedesirability of feeding each segment with the same total current is thatit may be easier to electrically to generate such a condition, and oncesuch equal total currents are maintained the segmental currents may notrequire individual measurements, simplifying the data acquisition task.In this application, segmental electrode areas are sequentiallyincreased to provide a decreasing sequence of current densities. Caremust be paid to assure current density uniformity across the electrodes,requiring a deeper insulating cavity.

[0084] Another means of obtaining different and well-controlled currentdensity on different segment without controlling this distribution byelectrical means is through the design of a cell that provides anon-uniform current distribution. Such design can be based on a slantedor a curved anode, or an electrode that forms different angles with thesidewalls, similar to the Hull cell. However, here, unlike e.g., theHull cell, we apply a segmented electrode and measure precisely thecurrent density on each segment. This provides

EXAMPLE 9

[0085] This example discusses the application of the invention disclosedherein to electrochemical processes involving multiple simultaneouselectrode reactions. One, particularly important embodiment of thisclass of processes is that of alloy plating. Here, multiple species,typically, but not always, metal ions, are reacted simultaneously from amixture in a common electrolyte to provide a deposit that consists ofmulti-constituents that typically form an alloy, a solid solution, or asolid mixture. Specific examples of industrial interest include, but arenot limited to, brass (copper-zinc alloy), perm alloy and othercompositions of iron-nickel, tin-nickel, tin-palladium, tin-gold, solderand other composition of tin-lead, nickel-zinc, among many others. Thisexample applies also to systems where one component may be a minorconstituent of the deposit, for example, when doping compounds or traceelements are used to impart to the deposit special properties. Examplesinclude, gold-cobalt and gold-nickel. Other examples of common multiplesimultaneous electrode reactions are manifested when plating additivesare used to provide special properties to the deposition process itself.Here often organic compounds, but occasionally, inorganic or metallictrace compounds are added to the electrolyte to affect the deposit color(e.g., nickel in gold, or chloride in copper), surface texture, (e.g.,sulfur compounds (‘additives’) in copper plating), or level the depositdistribution (e.g., polyethylene glycol (‘carrier’) in copper plating orsodium lignin sulfonate in lead plating). In all those cases, and inparticular in the alloy plating applications, it is very difficult todetermine the kinetics parameters of the different but simultaneouselectrode reactions. The reason being, that the co-deposition processincorporates interactions between the different participating species,which no longer behave as if they were undergoing the electrode reactionjust by themselves. These interactions are often quite significant, andin numerous situations, modify completely the expected results. Anexample is perm alloy (iron-nickel) plating, where the nickel platesmuch more readily than the iron, however, based on the single metalexperiments, the iron should plate preferentially. Accordingly, singlespecies deposition experiments are useless in providing data for thealloy deposition process. On the other hand, studying the depositionrates of the components during co-deposition is difficult, because onlythe total current can be measured, and the latter is notspecies-specific. Hence, one needs in addition to analyze the depositcomposition and deduce from the latter, the partial currents for thedeposition of each component. By itself this is not a very difficultprocedure if the required analytical instrumentation is available.However, since the partial currents are needed as a function of thecomplete current or voltage range which the process might experience,direct scanning is no longer an option, and a series of separatedeposition experiments is required to produce samples that span theentire range of interest. The invention disclosed herein, eliminates theneed for a series of experiments and provides, all at once, a number ofsamples (corresponding to the different segmented controlledelectrodes), where each has been plated at a single different currentdensity. Once compositional analysis of the different patches isperformed, the partial kinetics parameters, evaluated under interactiveconditions, can be readily calculated, following the procedures outlinedin example 1 for a single electrode reaction.

EXAMPLE 10

[0086] In the foregoing examples, the different current densities weregenerated by electrical means, i.e., electrical circuitry controlled thecurrent distribution. However, the cell configuration is another meansthat can be used advantageously to generate a varying currentdistribution. Unlike earlier disclosures, by e.g., Hull [U.S. Pat. No.2,149,344], we provide, however, precise means, using the segmentedelectrode approach, to measure the local current density, and use thisto correlate both the appearance of the deposit to the currentdistribution and to quantitatively evaluate the process parameters.Methods that can be used to generate a varying current density along aplurality of isolated electrodes, which are contemplated in the presentexample, include the use of a slanted or curved anode, a cell withvarying electrolyte gap, and resistive electrodes. The latter can beused either as anodes or cathodes, to produce a non-uniform currentdistribution.

EXAMPLE 11

[0087] Another manifestation of the invention, shown in a schematicdiagonal cross-sectional view in FIG. 9A, is a tabletop device. Thetabletop unit consists of four major parts: a container vessel (90), apatterned shielding mask (94), a test panel (91), and the electricalconnector assembly (100). FIG. 9B shows a side view of the device, withpartially transparent walls to show some key internal features. FIG. 9Cis a top view of a cross-section through the device as indicated by thedashed line A-A in FIG. 9B. FIG. 9D is a frontal view of the devicethrough the cross-section indicated by the dashed line B-B in FIG. 9B.FIG. 9E is a side view of the plating mask that is indicated by (94) inFIG. 9A. FIG. 9F is a side view of the test panel that is indicated by(91) in FIG. 9A. A more detailed description of the device follows.

[0088] The function of the container (90) is to provide space (110) forcontaining the tested electrolyte and to hold the device components inplace. The container, which is made from an electrically insulatingrigid material, e.g. cross-linked polyvinyl chloride (CPVC), consists ofa base plate (111), and four vertical side-walls (112) forming arectangular box that measures in this particular example about 1 inch inwidth (depth), 6 inches in length and 3 inches in height. Typically, thecontainer is larger in length than the plated panel, thus providing anon-occupied region (110) into which the tested electrolyte can beeasily poured. In this particular example, no cover is provided for thecontainer, although an optional cover may be incorporated as describedbelow.

[0089] The patterned mask (94 and FIG. 9E), consisting of an insulatingplate, in this example, ⅜″ thick CPVC, with a slot pattern (96) cut intoit. The mask is placed inside the container and is mounted against itsback wall using bolts (113). The slots expose predetermined regions ofthe metal pattern on the test panel (91) to the electrolyte. Thefunction of the mask is to restrict the plating current to certain,precisely determined regions on the test panel. Optional gaskets (97)can be used to separate the compartments formed by the mask to minimizeor eliminate current leakage and ‘cross-talk’ between the electrodesegments. Modeling and experiments indicate, however, that this‘cross-talk’ is negligible, and the gaskets can be eliminated withoutloss of noticeable accuracy.

[0090] An anode (99), which is a sheet metal, perforated metal, or ametal grid or mesh, made of e.g., titanium, platinum, platinizedtitanium, gold, ruthenium, or stainless steel, is facing the exposedsegments of the test panel. The anode is placed inside a groove on theback side of the mask and clamped between the mask and the sidewall. Theanode is connected via a non-dissolving conductor wire indicated as(121) in FIG. 9B, which is made of e.g., platinum, titanium or tantalum,and connected to a terminal (122) on the electrical connector (100).

[0091] The test panel (91, and FIG. 9F) is typically a customizedprinted circuit board, consisting of an insulating substrate (92, FIG.9F) onto which a conductive metal stripe pattern (93, 96, in FIG. 9F) isprinted or etched. The lower, broader pads of the pattern (93) getplated; the upper, narrower stripes (96) provide means for feeding thecurrent to the plated pads. Since the stripes are narrow, any portionthereof that is not masked and gets plated will not introduce a largeerror in terms of the measured current and the computed current density(=current per plated area). One or more pads, typically at the front endor the back end of the electrode array, may not be plated and usedinstead for sensing purposes, as a reference or sensing electrodes,providing a measurement of the electrolyte conductivity and/or thestandard potential of the plated metal. In this particular example, onepad out of seven, located at the front end of the pad assembly, is usedas a reference electrode. The metal pattern is typically made of copper.For characterizing the plating of metals other than copper, the copperpattern may be optionally pre-plated with other metals, matching thetype of plating solution to be tested. For example, in testing of nickelplating solutions, a nickel coating may be pre-applied onto the copper,or any other base metal, prior to testing. This, however, is notessential, because the substrate metal becomes coated with the platedmetal during the test itself. The pre-coated substrates may improve,however, the accuracy of the test.

[0092] The test panel (91) is inserted prior to the test into thecontainer (90) and pressed against the insulating mask (94) by aback-plate (95) made of a rigid insulating material, e.g., PVC, which ispushed and held in place using a screw (120) or a toggle clamp.

[0093] The electrical connector assembly (100) provides means forfeeding the plating current separately to each of the plated segments,and the sensing voltage to the sensing or reference electrodes, whenused. The electrical connector assembly consists of a multiplicity ofmetallic rod contacts (98) that are pressed against the metal stripes onthe test panel by means of springs (130), such that a separate rod makescontact with each of the metal stripes, feeding the current to theplated pads. Instead of springs, an elastomer strip may be applied atthe back of the rods and provide the required contact force. The currentfrom the anode is also fed through the electrical connector assembly. Inthis particular example, the anode current is fed through the mountingbolt (140) of the connector assembly. This bolt screws into a nut (122)in the container sidewall that is connected to the anode wire (121). Amulti-conductor cable (150) or ribbon feeds the currents from theconnector assembly through different magnitude resistors to the powersupply that is located within the main electrical box (not shown). Oncevoltage is applied, a different magnitude current is fed to each of thecontacts, resulting in a different plating rate on each of the platedelectrode pads that are exposed to the electrolyte through the mask. Foreasy insertion of the test panel and for convenient handling of thecontainer during electrolyte filling, removal, or rinsing, the entireconnector assembly can be removed by un-tightening two bolts (one shownin FIG. 9A, indicated as 140). To prevent upside-down re-assembly of theconnector, which will lead to improper connections, the holding boltsare designed asymmetrically, thus enabling assembly only in the properposition.

[0094] The electrical box can apply different currents and voltages tothe test panel, so that the current range matches the properties of thetested properties. Also, optionally, sequentially stepping or scanningthe current and voltages can expand the range of the measurements.

[0095] A typical test sequence consists of the following steps: (a)filling the container vessel with about 40 cm³ of electrolyte; (b)inserting a test panel; (c) tightening the clamping bolt thus pressing(via the back-plate) the test panel against the mask; (d) attaching theelectrical connector assembly; (e) turning on the power supply and thedata acquisition system.

[0096] A main advantage of the tabletop device described herein is thatthe electrical connections can be made above the electrolyte level, thuskeeping the electrical contacts free from corrosion and contaminationand eliminating the need for careful sealing. Furthermore, it can beused for testing small samples of electrolyte (less than 30 cm³) and canbe easily assembled, disassembled, and cleaned.

[0097] This configuration lends itself to conveniently enhancing theconvection by having gas (e.g., air) bubbled, or electrolyte circulatedthrough each of the segmental compartment, for testing the effects ofconvective flow on the plating process. To provide for the flow, narrowholes or slits can be drilled into the walls or bottom of the segmentalcompartments formed by the mask. The flow form the externally mountedpump can be entered at the bottom plate of the container and then besplit and directed into each of the plating compartments by drillingsmall holes in the mask at the bottom of each plating compartment. Theholes can be identical in size (for uniform flow rate) or of differentdiameter, to generate different flows in each compartment. The flow willegress at the top of the slots within the mask, will flow towards theback wall through a groove provided fro this application and willcollect at the empty region of the container, from which it can becirculated by the pump. Because of the small volume, smallcross-sectional areas, and small electrode areas, a small pump issufficient.

[0098] Temperature control can be provided by an immersion heater, andthe electrolyte temperature monitored using a thermocouple, a thermistoror a resistance thermometer (RTD). Also optionally, pH monitoring, ionsensing electrodes and/or electrolyte conductivity measurements can becarried out by inserting proper probe electrodes that are commerciallyavailable or that can be custom prepared, into the open region withinthe container where much of the electrolyte is held. The electricalcurrents for operating the heater, and the pump, and the signals fromthe sensors can be fed through the electrical connector assembly and thesame multi-wire cable that carries the plating current.

[0099] The tabletop device can be provided with a cover that willminimize electrolyte evaporation and splashing and also be helpful instabilizing the temperature. The cover which will fit over the containerwill have an appropriate slot to accommodate the insertion of the testpanel.

[0100] While the invention has been specifically illustrated anddescribed, those skilled in the art will recognize that the inventionmay be variously modified and practiced without departing from theconcepts of the invention.

I claim:
 1. An electrochemical device, comprising: a cell with aplurality of discrete cathodic or anodic regions at which one or moreelectrochemical reactions occurs; and means for causing the one or moreelectrochemical reactions at each of the plurality of discrete regionswhereby each of the one or more electrochemical reactions is measurableand quantifiable.
 2. The device of claim 1, wherein the means forcausing the one or more electrochemical reactions that occur at each ofthe plurality of discrete regions to be different.
 3. The device ofclaim 1, wherein the means for causing the one or more electrochemicalreactions at each of the plurality of discrete regions causes the one ormore electrochemical reactions to proceed simultaneously and for thesame amount of time.
 4. The device of claim 3, wherein the means forcausing the one or more electrochemical reactions cause the one or moreelectrochemical reactions to occur simultaneously at different currentdensities at each of the discrete regions.
 5. The device of claim 4,wherein the one or more electrochemical reactions cause a discretedeposit at each of the discrete regions, each discrete deposit being afunction of the current density at the discrete region of the discretedeposit.
 6. The device of claim 4, wherein each of the discrete regionsis disposed on a same substrate.
 7. The device of claim 5, including:means for measuring the current density at each of the discrete regionswhile the one or more electrochemical reactions occur simultaneously atdifferent current densities at each of the discrete regions.
 8. Thedevice of claim 7, including: means for measuring the voltage at each ofthe discrete regions while the one or more electrochemical reactionsoccur simultaneously at different current densities at each of thediscrete regions.
 9. The device of claim 1, wherein the electrochemicalreactions occur at different reaction rates that take place sequentiallyat the distinctly different anodic or cathodic regions.
 10. The deviceof claim 1, wherein the electrochemical reactions occur at differentreaction rates that vary in a periodic fashion at the distinctlydifferent anodic or cathodic regions.
 11. An electrochemical device forsimultaneously forming a plurality of electroplated deposits at aplurality of discrete cathodic or anodic regions at which one or moreelectrochemical reactions occurs; the electrochemical device comprising:a cell and a plated, segmented substrate, the substrate having disposedtherebetween a plurality of discrete cathodic or anodic regions at whichone or more electrochemical reactions occurs.
 12. The electrochemicaldevice of claim 11 wherein the substrate is constructed of a dielectricmaterial selected from the group comprising silicon, glass and plasticmaterial.
 13. The electrochemical device of claim 12 wherein thesubstrate has a conductive seed layer formed thereon, the conductiveseed layer being constructed of a material selected from the groupcomprising of copper, nickel, brass, gold, and other conductivematerials compatible with an electrochemical process.
 14. Theelectrochemical device of claim 13 wherein the substrate has aconductive seed layer formed as a continuous conductive layer.
 15. Theelectrochemical device of claim 14 wherein the substrate has aconductive seed layer formed by a vapor phase process, an electrolessprocess, by lamination or gluing a conductive film onto the dielectricsubstrate.
 16. The electrochemical device of claim 15 wherein thesubstrate has a conductive seed layer segmented into a plurality ofdiscrete, electrically isolated sections.
 17. The electrochemical deviceof claim 16 wherein the substrate has a conductive seed layer issegmented into a plurality of discrete, electrically isolated sectionsby grooves cut through the conductive seed layer between each of thediscrete sections.
 18. The electrochemical device of claim 11, whereinthe substrate comprises a patterned printed circuit board having apattern thereon that provides the plurality of discrete electricallyisolated sections.
 19. The electrochemical device of claim 14 whereineach of the plurality of discrete electrically isolated sections has aseparate electrical contact attached thereto.
 20. The electrochemicaldevice of claim 19 further including means for directing a differentcurrent through separate current paths to or from each of the separateelectrical contacts.
 21. The electrochemical device of claim 20 furtherincluding resistors in each of the separate current paths to control thecurrent to each separate electrical contact.
 22. The electrochemicaldevice of claim 1 wherein one or more of the discrete cathodic regionsor anodic regions forms a reference electrode adapted to measure thepotential in the electrolyte at the position where the referenceelectrode is located.
 23. The electrochemical device of claim 11 whereinthe cell incorporates an enclosure with a plurality of cavities therein,each cavity corresponding to one of the discrete cathodic or anodicregions whereby when the cell is assembled each of the discrete cathodicor anodic regions is exposed to an electrolyte and ionic current. 24.The electrochemical device claim 23 wherein the depth of the cavitiesensure a uniform current density across the discrete cathodic or anodicregions formed on the substrate.
 25. The electrochemical device of claim11 wherein a counter electrode is not segmented and is disposed at afixed distance from the substrate.
 26. The electrochemical device ofclaim 25 wherein the substrate is a cathode, and the counter electrodeis an anode formed of a material on which oxygen can evolve.
 27. Theelectrochemical device of claim 26 wherein the anode is formed of aconductor selected from the group comprising platinum, gold, titanium,titanium coated with iridium oxide, ruthenium oxide, platinum, lead, orsilver-lead alloy, and solubles such as copper and nickel.
 28. Theelectrochemical device of claim 11 wherein: the substrate is selectedfrom the group including a segmented rotating disk electrode and arotating segmented disk electrode surrounded by a ring electrode. 29.The electrochemical device of claim 11 wherein: a central circularelectrode that is not segmented; and the substrate is a surroundingelectrode that is segmented to provide a plurality of electrodes. 30.The electrochemical device of claim 11 further including means foragitating or circulating the electrolyte, the means for agitating orcirculating selected from the group comprising inert gas for agitation,air bubbling for agitation, a stirrer, and a pump.
 31. A process fordetermining the quality of electroplated deposits comprising:simultaneously depositing a plurality of discrete deposits, each depositat one of a plurality of discrete cathodic or anodic regions at whichone or more electrochemical reactions occurs; and causing the one ormore electrochemical reactions at each of the plurality of discreteregions whereby each of the one or more electrochemical reactions ismeasurable and quantifiable.
 32. The process of claim 31 wherein the oneor more electrochemical reactions that occur at each of the plurality ofdiscrete regions is different from the other reactions.
 33. The processof claim 31 wherein each of the one or more electrochemical reactions ateach of the plurality of discrete regions proceeds simultaneously andfor the same amount of time.
 34. The process of claim 31 wherein the oneor more electrochemical reactions occur simultaneously at differentcurrent densities at each of the discrete regions.
 35. The process ofclaim 34 wherein the one or more electrochemical reactions cause adiscrete deposit at each of the discrete regions, each discrete depositbeing a function of the current density at the discrete region of thediscrete deposit.
 36. The process of claim 35 including the step ofmeasuring the current density at each of the discrete regions while theone or more electrochemical reactions occur simultaneously at differentcurrent densities at each of the discrete regions.
 37. The process ofclaim 35 including the step of measuring the voltage at each of thediscrete regions while the one or more electrochemical reactions occursimultaneously at different current densities at each of the discreteregions.
 38. A method for calculating electrochemical process parametersin an electrochemical device having a plurality of distinctly differentcathodic or anodic regions including: measuring currents and voltageswhile at least one electrochemical reaction takes place at differentmeasurable rates on a plurality of distinctly different cathodic oranodic regions in the electrochemical device.
 39. The method of claim 38wherein the different reaction rates take place simultaneously on thedistinctly different cathodic or anodic regions.
 40. The method of claim38, wherein the process parameters are selected from the groupcomprising the polarization curve and the kinetics constants of theelectrochemical reaction.
 41. The method of claim 38, wherein theparameters are selected from the group comprising the electrolyteconductivity and the equilibrium potential.
 42. The method of claim 38wherein the electrochemical process parameters are comprised of thereactant ion diffusivity.
 43. The method of claim 38, wherein theplurality of reactions on each region are comprised of two primaryreactions, one a deposition reaction and one a gas evolution reaction.44. The method of claim 38 wherein calculating electrochemical processparameters includes: weighing or measuring the thickness of the deposit;and quantitative characterization of the current efficiency as functionof the overall current or voltage.